Integument Flashcards
1
Q
What are the functions of the integument?
What are the epidermal derivatives contained within the integument?
A
- barrier for protection, sensation, excretion, thermoregulation, and vitamin D3 synthesis
- contains hair, nails, sebaceous and sweat glands
2
Q
What are the layers of integument?
A
- epidermis: epithelial layer (ectoderm derived)
- dermis: layer of CT (paraxial mesoderm > dermatome derived)
- hypodermis (subcutaneous): loose CT layer, binds the skin to underlying tissue and corresponds to the superficial fascia
3
Q
What epithelium type is the epidermis?
What are the main types of cells within the epidermis?
A
- epidermis consists mainly of stratified squamous keratinized epithelium
- composed mostly of keratinocytes; less abundant are melanocytes, Langerhands cells, and Merkel cells
4
Q
- irregular projections at epidermal-dermal junction
- interdigitate w/ epidermal ridges to strengthen adhesion = increased anchoring of epidermis to dermis
A
dermal papillae
5
Q
What are the two types of skin?
A
- thick (400-1400 μM): palms and soles, fiver layers (w/ stratum lucidum), fingerprints
- thin (75-150 μM): widespread on body, four layers, glands and hair follicles
6
Q
What are the 4-5 layers of skin?
A
- stratum corneum (SC)
- stratum lucidum (not shown in image)
- stratum granulosum (SGr)
- stratum spinosum (SS)
- stratum basale (SB)
*know these in order, know distinguishing features, be able to identify them individually*
7
Q
- 15-20 layers of squamous, keratinized cells of the epidermis, filled w/ filamentous keratins
- cells are anucleate (more space for keratin) and coated by an extracellular layer of lipids (from granules of SGr)
- fully keratinized “cornified” cells, squames, are continuously shed as desmosomes break down
A
stratum corneum
8
Q
- layer of the epidermis found only in thick skin
- thin, translucent layer of flattened eosinophilic keratinocytes
- held together by desmosomes
- nuclei and organelles have been lost
- cytoplasm is almost exclusively keratin filaments
A
stratum lucidum
9
Q
- three to five layers of flattened cells of the epidermis
- filled w/ keratohyaline granules (granules = tonofibrils + filaggrin (bundling protein)): undergoing terminal differentiation of keratinization, stain intensely basophilic
- also include lamellar granules (small, ovoid structures containing lipids and glycolipids): undergo exocytosis and produce lipid-rich, impermeable layer that protects against water loss
- keratinization + lipid-rich layer = almost impenetrable skin barrier
A
stratum granulosum
10
Q
- typically the thickest layer of epidermis
- polyhedral cells w/ central nuclei and spiny processes
- keratin filaments assemble here into microscopically visible bundles called tonofibrils (a/w desmosomes > result in spiny appearance ‘prickle layer’)
A
stratum spinosum (remember ‘spiny’)
11
Q
- layer of the epidermis
- single-layer of keratinocytes w/ stem cells interspersed
- mitotically active, cuboidal/low columnar cells
- contains melanin and melanocytes
- bound apically by desmosomes
- bound basally by hemidesmosomes
A
stratum basale
12
Q
What does the mnemonic C’mon Let’s Get Sun Burn stand for?
A
(layers of the epidermis from apical to basal)
- Corneum
- Lucidum
- Granulosum
- Spinosum
- Basale
13
Q
- predominant cell type of the epidermis
- produce keratins, 85% of cells within the epidermis
- participate in the epidermal water barrier
- will produce “cornified” cells (full of keratin)
- stratum corneum is when keratinocytes are most mature
- outermost layer of skin, we lose these with abrasion
- undergo keratinization and desquamation (loss of cells)
A
keratinocytes
14
Q
- type of cell within the epidermis
- produce melanin and transfer it to keratinocytes
- melanin: pigment protein that protects nuclei from UV radiation
- neural crest-derived, scattered along stratum basale
- epidermal-melanin unit: one melanocyte maintains an association w/ a specific number of keratinocytes (1:10)
A
melanocytes
15
Q
Describe the process of melanin production:
A
- tyrosinase coverts tyrosine > DOPA (3,4-dihydroxyphenylalanine)
- DOPA is polymerized to melanin
- reactions occur in membrane-bound organelles, premelanosomes
- as melanin increases in premelanosomes, a melanosome is produced
- melanosomes are transferred to keratinocytes (pigment donation)
- creates a melanin umbrella that shields the nucleus
17
Q
- antigen presenting cells (APCs) that provide defense against pathogens (develop from monocyte precursor)
- identifiable in stratum spinosum
- pale cytoplasm w/ long processes
- antigen is phagocytized and displayed on the cell surface
- cell migrates to a nearby lymph node to activate lymphocytes
A
Langerhans cells
18
Q
How are epidermal cells differentiated and replaced?
A
- replacement is initiated by the division of stem cells in the stratum basale
- new cells undergo divisions in the stratum basale
- move upward as they differentiate into keratinized cells
- eventually are lost by exfoliation on skin surface
19
Q
- uneven boundary with finger-like dermal papillae that project into epidermis
- complemented by epidermal protrusions, epidermal ridges
- increased in size/number at sites of mechanical stress
- hemidesmosomes provide tight interface
- focal adhesions are also present
A
dermal-epidermal junction
20
Q
What are the 2 layers of the dermis?
A
- papillary layer: loose CT immediately beneath epidermis, vasculature and nerve endings present
- reticular layer: deep to papillary layer, dense irregular CT w/ coarse elastic fibers, form regular lines of tension (Langer’s lines) that are important for surgical purposes
22
Q
- loose CT that binds the skin loosely to the subjacent organs
- adipocytes vary in number and size based on body regions/nutritional state
- extensive vasculature promotes rapid uptake of insulin or drugs injected into this tissue
A
hypodermis (subcutaneous fascia)
23
Q
- epithelial tactile cells that function as low threshold mechanoreceptors essential for sensing gentle touch
- abundant in highly sensitive skin (fingertips, hair follicles)
- resemble surrounding keratinocytes but lack melanosomes
- contain small, golgi-derived granules concentrated near basolateral surface
A
Merkel cells
25
Q
- located in the papillary dermis and extending into lower epidermal layers
- respond primarily to high and low temperatures, pain, and itching
- may also function as tactile receptors
A
free nerve endings
26
Q
- encapsulated receptors responsive to light touch or low frequency stimuli
- perpendicular to the epidermis (located in the tip) in the dermal papillae
- numerous in fingertips, palms, and soles
A
Meissner’s capsule
27
Q
- large, encapsulated, oval structures found deep in the reticular dermis and hypodermis
- specialized for sensing coarse touch, pressure (sustained touch), and vibration
- also found in CT of visceral organs (wall of rectum and urinary bladder) to produce pressure sensations when distorted
A
lamellated (pacinian) corpuscle
28
Q
- type of gland
- secretion delivered via membrane bound vesicles and undergo exocytosis
A
merocrine gland
29
Q
- type of gland
- secretion accumulates within cell, apoptosis secretion and cell debris released
A
holocrine gland
30
Q
- type of gland
- release of apical portion of the cell, surrounded by cytoplasm within a plasma membrane
A
apocrine gland
31
Q
- several glands per follicle
- abundant on face and scalp
- produce a lipid mixture, sebum via holocrine secretion
- waxy mix of trigs and cholesterol (lubricates and softens skin, waterproofs skin)
- sebum discharged into hair follicle
A
sebaceous glands
32
Q
- simple, coiled glands found extensively throughout skin
- duct is stratified cuboidal
- myoepithelial cells facilitate expulsion of secretions via merocrine glands
- temperature regulation via cooling (evaporation of H2O from sweat on body surface)
- sweat components: H20, salt, ammonia, uric acid, and mucinogen granules
A
eccrine sweat glands
33
Q
- large lumen, tubular glands
- duct is stratified cuboidal
- myoepithelial cells facilitate expulsion of secretions via merocrine secretion
- protein, carbohydrates, and ammonia rich secretion
- odorless until mixed w/ bacteria
- become functional at puberty and is what makes pubescent kids smelly
A
apocrine sweat glands
34
Q
What is the structure of hair follicles?
A
- hair follicle has a terminal dilation called a hair bulb
- dermal papilla inserts into hair bulb, provides nutrients via capillaries
- keratinocytes form the hair matrix: continuous w/ epidermis, divide and differentiate which creates hair growth
- follicular bridge: contains epidermal stem cells, near insertion of arrector pilli M.
- arrector pilli M.: small bundle of smooth muscle that extends from midpoint of hair root to papillary layer (dermis); goose bumps = contracting muscle distorts attached dermis
